BY SIMPLY DRAWING A CUBE, you can understand some of the significance of line in creating the illusion of reality. It seems evident at once that the outer lines symbolize the edges of the cube and the inner lines symbolize the place where planes meet upon the cube. Now if you wish to indicate a spot of colored ink upon the cube, you will find yourself drawing a line around the edges of the spot to symbolize its presence. In other words, it will be seen at once that lines may be used to symbolize the outer edges of an object, the meeting of planes, and the meeting of one color and another. And, of course, a line may be used to symbolize a line!
Let us take these things up one by one. If you decide to make a line drawing of an object without any interior details, you might say that the line symbolizes the place where the background stops and the object begins. If you draw a profile of a head against a wall, the line differentiates head from wall, and incidentally creates the illusion that the head is in front of the wall — even though your paper is absolutely flat! I think this is well understood by everybody, so let us move on to a much more subtle matter: the use of line to indicate the meeting of planes.
In drawing a cube, you automatically put a line where the various faces of the cube meet. This shows how well a line symbolizes the place where plane meets plane. You can understand, then, why an artist who draws a building makes a line where one wall meets another wall. He also draws a line where the top of a table meets the side of the table. Thus, he draws lines to show the meeting of exterior planes.
Now, if you can visualize yourself inside a cube, you can understand why the artist puts a line where a ceiling meets a wall, where a floor meets a wall, or where wall meets wall. This is the meeting of interior planes.
If you draw a cylinder with a flat top, you will find yourself drawing a line where a curved plane meets a flat plane. Someday you will realize that you are drawing a line where a curved plane meets a curved plane when you draw the breast meeting the rib cage, for instance, or the buttock meeting the back of the thigh.
When one color abruptly meets another color, a line may be drawn to symbolize this meeting. If you wished to make a line drawing of the flag, you would draw a line around the blue area, a line around each red area, and a line around each white area. For the eye, you might well draw a circle where the colored iris meets the white, plus a smaller circle where the dark pupil meets the iris.
You must remember that an artist thinks of shade and shadow as color, so when a dark area abruptly meets a light area, a line is often used to symbolize this meeting. If you put a white block (or cube) near a window, you will see that each plane of the block has a different degree of lightness or darkness — a different tone. When you draw the block you will use a line to indicate the meeting of these light and dark planes.
A further use of line is to explain more fully the shape of the form over which the line moves. If drapery is striped, for instance, a careful rendering of the stripes more fully explains the form of the drapery. Instructors are forever recommending that the student throw a piece of drapery over a chair and draw it. This is wonderful practice. The more stripes, the better; a Scottish plaid is ideal.
It is also very good practice to draw a cake of ice and then draw lines over it; since ice is transparent, you will have to draw the lines on the back of the ice too. Draw a transparent cylinder, and draw a spiral line around the front and back. Draw a transparent globe, and run lines of latitude and longitude around it.
Not only is the shape of the object more fully explained by this process, but the practice increases your feeling for form. Eventually the surface of your paper seems to become transparent: your lines seem to recede from you and approach you as you draw.
In figure drawing, in order to clarify the shape of the form, the artist is forever seeking lines that move across the skin. It is too bad that human beings are not striped like zebras, because then it would be very easy to explain the shape of the nude. But since they are not, the artist is forever seeking and even inventing such lines in his search for the illusion of form. He invents all kinds of lines he cannot see at all. This, I assure you, takes a thorough knowledge of the elements of drawing. The accomplished artist, for instance, will run an imaginary ribbon around the neck; furrow the placid forehead; invent the meeting of planes, and draw lines where these planes meet. If he is shading with lines, he will be altogether conscious that the direction of these lines may be used to accentuate the shape and direction of the form over which they travel. The study of artistic anatomy is of great value in determining which lines to accentuate on the human body and which to subordinate or leave out. Muscles, for instance, are often in groups related by function; lines are used to separate the groups rather than the individual muscles.
As I have suggested, it is a great help to run lines over simple geometrical forms. Running lines over the nude is much more difficult, but a marvelous aid in helping you to understand the shape of the body. These lines are called contour lines. One way to think of a contour line is to imagine the track left by a very small insect with ink on his feet crawling over the nude. It is said that as soon as you can run contour lines perfectly in any direction over any part of the body, you have really learnt how to draw. Many difficult problems in drawing are readily solved by a full understanding of the contour line: the exact placement of the eyes on a three quarter view of the head, for example, and the transference of a likeness from profile to the three quarter head.
Line is further used to suggest the changing tones of light and shade that lie upon an object. A line of varying strength can be run across an object: where the line is heavy, it will suggest deep shade on the object; where it is light, the line will suggest light shade; if the line is very light or absent, it will suggest a highlight.
Naturally, we will have more to say about line, especially in relation to planes, light and shade, and direction. But enough has been said already for you to realize that line has many functions, and that sometimes a simple line may indicate not one, but many of the conditions I have just described.
When you are drawing a head, think for a moment of the line that designates the top limit of the upper lip. This line symbolizes not only the change in planes where the lip meets the skin above. It also shows the color change where the red of the lip meets the skin; the shape of the form over which the line moves; the abrupt change of dark to light where the down plane of the lip meets the up plane above; and finally, the movement of light and shade upon the head as a whole.